As part of an effort to make home life more convenient, safe, and entertaining, home automation products have been developed. These products enable the home owner to perform and monitor various tasks in an automated or semi-automated fashion. A wide range of tasks are feasible involving assorted systems of the home including the lighting, climate control, security, maintenance, and entertainment systems, among others. Home automation also enables the integration of systems that may not have historically been integrated and the remote control of systems that may not have historically been remotely controlled. For example, with proper equipment and set up, it would be possible with one push of a button to close the drapes if it was too bright outside, dim the lights if it was too bright inside, turn on the television if it was not already on, turn on the surround sound tuner if it was not already on, turn on the DVD player if it was not already on, place the television in the proper video mode, place the tuner in the proper audio mode, and start a DVD playing. Both less complicated and even more complicated examples also exist using the same or different systems individually or in combination.
Generally, a home automation system includes a central processor, a plurality of controllers, and some means of communicating between and among the central processor and the controllers. The controllers may also perform some data collection and processing. In one such system, the communication is carried over the power lines of the dwelling. This allows the system to be retrofitted into an existing structure with less inconvenience and expense. The central processor and controllers each form modules that are coupled to the power lines through the power receptacles of the residence. The modules communicate with one another by way of signals placed on the power lines. A communications protocol exists whereby transmitters transmit messages and receivers receive messages. Each module may be a transmitter, a receiver, or both. Each module may have at least some user interface. The user interface may be as simple as a power receptacle or a switch. By necessity, the user interface for the central processor may be much more complicated. It is also possible for a module to be connected to an external user interface such as a personal computer and the like. The computer may also perform command and control functions. Connecting the home automation system to the computer takes advantage of an existing and familiar user interface and the processing and connectivity power of the computer. The module may only be temporarily connected to the external user interface. The connection period may also be more prolonged depending on the circumstances.
Among the more conventional means of connecting a module to an external user interface such as a computer is through an industry standard often referred to as RS232. The RS232 communications protocol is a well known serial data link between devices. Despite this fact, it is not always followed exactly as presented by the Electronic Industries Association. Over the over thirty years since this standard was developed, the EIA has published three modifications with the most recent being the EIA232E standard introduced in 1991. Besides changing the name from RS232 to EIA232, some signal lines were renamed and various new ones were defined, including a shield conductor. The point of connection at each device is referred to as a communications port. The protocol does not include provisions for one device to supply any significant amount of power over the link to other devices to which it is connected. Consequently, each device must include an internally powered communications port. Traditionally, this has not presented a major obstacle in the home automation environment as each module was already connected to the power lines of the home for communication with other modules in the system. It is important to note however that the module power supply must be an isolated one to prevent potential electrical problems with the connection between the module and the computer. Other non-powered communications protocols similar to that of RS232/EIA232 exist as well.